During the last 30 years, the technology of fluorescence-activated cell sorting has enabled countless breakthroughs in many fields. In an exciting technological leap, this concept has recently been extended to include sorting of large cells, cellular particles, and even whole organisms by the Complex Object Parametric Analyzer and Sorter (COPAS) instrument. This emerging technology has already had significant impact in the model organism C. elegans, and recently investigators at the Joslin Diabetes Center have worked with the COPAS manufacturer (Union Biometrica) to optimize its use for large mammalian cells or aggregates (adipocytes, embryoid bodies, pancreatic cell aggregates, and others). This work has been performed on demonstration instruments that were placed temporarily in the Flow Cytometry Core facility at Joslin. As this technology optimization phase had now been completed, those instruments will be removed by the company before the end of Summer, 2009. We propose here to purchase a COPAS BIOSORT instrument that will be placed in the Joslin Flow Cytometry Core permanently. That instrument will be used to facilitate and expand research efforts that were initiated on the temporary demonstration machines. The COPAS to be purchased will be used to sort C. elegans, the mammalian cell types listed above, hematopoietic stem/niche cell aggregates, and retinal microvessels. The vast majority of these planned projects are NIH-funded. It is expected that this instrument will be used heavily, as it will be the only one of its kind in the Longwood Medical Area of Boston, which includes Harvard Medical School and many of its major affiliated hospital research facilities.